JP2012133156A - Optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film formed from an acrylic resin composition, which is capable of realizing large phase difference due to an unconventional composition and also suppressing generation of a seeming or optical defect in production and use.SOLUTION: The optical film of the present invention is formed from an acrylic resin composition containing 90 to 99.5 pts.mass of an acrylic resin having a ring structure in the main chain and 0.5 to 10 pts.mass of an amorphous ester polymer having a weight average molecular weight of 500 or more and 5000 or less. The optical film can be excellent in heat resistance by having the ring structure in the main chain and can be excellent in properties as a phase difference film by containing the amorphous ester polymer.

Description

  The present invention relates to an optical film made of an acrylic resin composition.

  An optical film obtained by stretching a film (original film) made of a thermoplastic resin exhibits various optical properties based on the orientation of polymer chains generated by stretching. One type of such an optical film is a retardation film utilizing birefringence generated by the orientation of polymer chains. Retardation films are widely used in image display devices such as liquid crystal display devices (LCDs). In recent years, thinning of image display devices has been strongly demanded, and in order to meet these demands. A thin retardation film showing a large retardation is desired.

  Acrylic resin represented by polymethyl methacrylate (PMMA) has high light transmittance and low photoelasticity, and has excellent optical properties, and also has a balance of mechanical strength, moldability and surface hardness. It is excellent and suitable as a thermoplastic resin used for a retardation film. However, the acrylic resin is difficult to produce a retardation film showing a large retardation because it is less likely to cause a retardation due to stretching than other thermoplastic resins generally used as a retardation film, such as a polycarbonate resin and a cycloolefin resin. .

  Japanese Unexamined Patent Application Publication No. 2008-9378 (Patent Document 1) discloses a retardation film mainly composed of an acrylic resin having a lactone ring structure in the main chain. Although depending on the type of the ring structure, the retardation exhibited by the retardation film is improved by including an acrylic resin having a ring structure in the main chain. Moreover, since the glass transition temperature of an acrylic resin improves with a ring structure, it can be set as the phase difference film excellent in heat resistance. According to Patent Document 1, a retardation film showing a larger retardation can be obtained by increasing the content of the ring structure in the acrylic resin. However, since the acrylic resin tends to be “hard” and “brittle” due to the ring structure entering the main chain, and it becomes difficult to sufficiently stretch the original film, there is a limit to improving the phase difference only by introducing the ring structure. Moreover, the film which became hard and brittle is easy to be damaged at the time of bending or torn at the time of handling, and the content of the ring structure cannot be increased unnecessarily.

  By the way, in Patent Document 1, it is described that a low molecular substance having the same sign as the intrinsic birefringence sign indicated by the acrylic resin may be added to the retardation film for the purpose of further improving the retardation indicated by the retardation film. Examples of low-molecular substances include stilbene, biphenyl, diphenylacetylene, and liquid crystal substances. Thus, the addition of the retardation increasing agent is expected to improve the retardation exhibited by the retardation film.

  Japanese Patent Application Laid-Open No. 2006-241197 (Patent Document 2) describes a low molecular compound containing two or more aromatic rings as such a retardation increasing agent, and examples of the low molecular compound include biphenyl and dihydroxybiphenyl. , Diphenyl sulfide, bisphenol, stilbene, diphenylacetylene, azobenzene and the like are exemplified.

  On the other hand, as a method of improving the strength of the film, there is a method of increasing the molecular weight of the resin. However, when a resin having a high molecular weight is melt-molded, the fluidity is lowered, and thus filtration is essential for optical applications. The process becomes difficult, and in order to increase fluidity, there arises a problem that the resin is colored when molded at a higher temperature.

  In order to solve such problems, Japanese Patent Application Laid-Open No. 2010-243581 (Patent Document 3) reduces bleeding out by adding a specific phosphorus compound to an acrylic resin having a lactone ring structure in the main chain. It describes that the fluidity at the time of melt molding can be improved.

JP 2008-9378 A JP 2006-241197 A JP 2010-243581 A

However, these low molecular weight compounds described in Patent Document 2 have a problem in compatibility with acrylic resin, and in particular, when forming an original film by melt molding, foaming and bleed out during molding at a high temperature. Such problems are likely to occur. In addition, when used as a retardation film after production, when heat is applied, such as when placed near the light source in an image display device, the low molecular weight compound bleeds out to improve the appearance or optically. Are likely to suffer.
Moreover, although the phosphorus compound described in Patent Document 3 has little bleed-out, it does not have a function of improving the phase difference characteristics.

  The present invention has been made in view of the above-described situation, and a large phase difference can be realized by an unprecedented composition, and the appearance or optical defects during manufacture and use are suppressed, and the phase difference is achieved. An object of the present invention is to provide an optical film having both film characteristics and film strength.

  The optical film of the present invention comprises an acrylic resin (A) having a ring structure in the main chain of 90 to 99.5 parts by mass, and an amorphous ester polymer (B) of 0.5 to 10 masses having a weight average molecular weight of 500 to 5000. It consists of an acrylic resin composition containing parts.

  In the optical film of the present invention, the amorphous ester polymer (B) is preferably an ester having an aromatic ring structure.

  In the optical film of the present invention, the amorphous ester polymer (B) is preferably an ester having an alicyclic structure.

  The optical film of the present invention preferably has a total light transmittance measured in accordance with JIS K7361-1 of 80% or more and a haze measured in accordance with JIS K7136 of 5% or less.

  The optical film of the present invention may be a stretched film.

  The optical film of the present invention may be a retardation film.

  The optical film of the present invention is preferably a retardation film satisfying Re (447) / Re (590) <1. [However, Re (447) and Re (590) are in-plane retardations of the optical film measured at measurement light wavelengths of 447 nm and 590 nm, respectively].

  The manufacturing method of the optical film of this invention is a manufacturing method of the optical film formed by melt-casting the said acrylic resin composition which passed through the melt filtration process.

  According to the present invention, an optical film having few appearance defects such as coloring and bleeding out, improved heat resistance and film strength, and excellent optical properties as a retardation film can be provided.

  In the following description, unless otherwise specified, “%” means “% by mass”, “parts” means “parts by mass”, and “A to B” representing a range means “A or more and B or less”. To do.

[Acrylic resin (A)]
The acrylic resin (A) is not particularly limited as long as it has a ring structure in the main chain.

  The acrylic resin is a resin having a (meth) acrylic acid ester unit and / or a (meth) acrylic acid unit as a structural unit, and is derived from a (meth) acrylic acid ester or a derivative of (meth) acrylic acid. You may have a unit. The total of the proportions of the structural units derived from the (meth) acrylic acid ester unit, the (meth) acrylic acid unit and the derivatives in all the structural units of the acrylic resin is usually 50% by mass or more, preferably 60% by mass. As mentioned above, More preferably, it is 70 mass% or more. In addition, when the main chain has a ring structure that is a derivative of a (meth) acrylic acid ester unit such as a lactone ring structure, the proportion of the (meth) acrylic acid ester unit and the (meth) acrylic acid unit in all the structural units, The sum total with the content rate of a ring structure should just be 50 mass% or more.

  (Meth) acrylic acid ester units are, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, t- (meth) acrylic acid t- Butyl, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, benzyl (meth) acrylate, dicyclopentanyloxyethyl (meth) acrylate, (meth) acryl Dicyclopentanyl acid, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, (meth) acrylic acid 2, 3,4,5,6-pentahydroxyhexyl, 2,3,4,5-tetrahydro (meth) acrylic acid Shipenchiru is a structural unit derived from 2- (hydroxymethyl) acrylate, 2- (hydroxymethyl) acrylate, a monomer such as 2- (hydroxyethyl) acrylate.

  The (meth) acrylic acid unit is a structural unit derived from a monomer such as acrylic acid, methacrylic acid, crotonic acid, 2- (hydroxymethyl) acrylic acid, 2- (hydroxyethyl) acrylic acid, and the like.

  The acrylic resin (A) may have two or more of these structural units as a (meth) acrylic acid ester unit and a (meth) acrylic acid unit. The acrylic resin (A) preferably has a methyl methacrylate unit. In this case, the thermal stability of a film obtained by molding the composition containing the acrylic resin (A) and the acrylic resin (A) is improved.

  The glass transition temperature (Tg) of the acrylic resin (A) is preferably 110 ° C. or higher. Since Tg as a resin composition can be improved, Tg of acrylic resin (A) is more preferably 115 ° C or higher, further preferably 120 ° C or higher, and particularly preferably 130 ° C or higher. Note that Tg of polymethyl methacrylate (PMMA) which is a typical acrylic resin is 105 ° C.

  When the acrylic resin (A) has a ring structure in the main chain, the Tg of the acrylic resin (A) and the resin composition is increased, and the heat resistance of the resin molded product obtained from the composition is improved. An optical member such as a resin molded product obtained from a resin composition containing an acrylic resin (A) having a ring structure in the main chain, such as a film, can be easily placed near a heat generating part such as a light source in an image display device. It is suitable for the use as.

  Although the kind of ring structure is not specifically limited, For example, it is at least 1 sort (s) chosen from lactone ring structure, glutaric anhydride structure, glutarimide structure, N-substituted maleimide structure, and maleic anhydride structure.

  The following general formula (1) shows a glutaric anhydride structure and a glutarimide structure.

上記一般式（１）におけるＲ^１、Ｒ^２は互いに独立して水素原子、またはメチル基であり、Ｘ^１は酸素原子または窒素原子である。Ｘ^１が酸素原子であるとき、Ｒ^３は存在せず、Ｘ^１が窒素原子のとき、Ｒ^３は、水素原子、炭素数１から６の直鎖アルキル基、シクロペンチル基、シクロヘキシル基またはフェニル基である。

In the general formula (1), R ¹ and R ² are each independently a hydrogen atom or a methyl group, and X ¹ is an oxygen atom or a nitrogen atom. When X ¹ is an oxygen atom, R ³ does not exist, and when X ¹ is a nitrogen atom, R ³ is a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, a cyclopentyl group, a cyclohexyl group, or a phenyl group. It is.

When X ¹ is an oxygen atom, the ring structure represented by the general formula (1) is a glutaric anhydride structure. The glutaric anhydride structure can be formed, for example, by subjecting a copolymer of (meth) acrylic acid ester and (meth) acrylic acid to dealcoholization cyclocondensation in the molecule.

When X ¹ is a nitrogen atom, the ring structure represented by the general formula (1) is a glutarimide structure. The glutarimide structure can be formed, for example, by imidizing a (meth) acrylic acid ester polymer with an imidizing agent such as methylamine.

  The following general formula (2) shows a maleic anhydride structure and an N-substituted maleimide structure.

上記一般式（２）におけるＲ^４、Ｒ^５は互いに独立して水素原子、またはメチル基であり、Ｘ^２は酸素原子または窒素原子である。Ｘ^２が酸素原子であるとき、Ｒ^６は存在せず、Ｘ^２が窒素原子のとき、Ｒ^６は、水素原子、炭素数１から６の直鎖アルキル基、ベンジル基、シクロペンチル基、シクロヘキシル基またはフェニル基である。

In the general formula (2), R ⁴ and R ⁵ are each independently a hydrogen atom or a methyl group, and X ² is an oxygen atom or a nitrogen atom. When X ² is an oxygen atom, R ⁶ is not present, and when X ² is a nitrogen atom, R ⁶ is a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, a benzyl group, a cyclopentyl group, a cyclohexyl group. Or it is a phenyl group.

When X ² is an oxygen atom, the ring structure represented by the general formula (2) is a maleic anhydride structure. The maleic anhydride structure can be formed, for example, by copolymerizing maleic anhydride and (meth) acrylic acid ester.

When X ² is a nitrogen atom, the ring structure represented by the general formula (2) is an N-substituted maleimide structure. The N-substituted maleimide structure can be formed, for example, by polymerizing an N-substituted maleimide such as phenylmaleimide and a (meth) acrylic acid ester.

  In each method for forming the ring structure exemplified in the description of the general formulas (1) and (2), all polymers used for forming each ring structure have a (meth) acrylate unit as a single unit. The resin obtained by this method is an acrylic resin.

  The lactone ring structure that the acrylic resin (A) may have in the main chain is not particularly limited, and may be, for example, a 4- to 8-membered ring. Alternatively, a 6-membered ring is preferable, and a 6-membered ring is more preferable. The lactone ring structure which is a 6-membered ring is, for example, the structure disclosed in Japanese Patent Application Laid-Open No. 2004-168882, but the lactone ring structure is high due to the high polymerization yield of the precursor and the cyclization condensation reaction of the precursor. A structure represented by the following general formula (3) is preferable because an acrylic resin (A) having a ring content can be obtained and a polymer having a methyl methacrylate unit as a constituent unit can be used as a precursor.

上記一般式（３）において、Ｒ^７、Ｒ^８およびＲ^９は、互いに独立して、水素原子または炭素数１から２０の範囲の有機残基である。当該有機残基は酸素原子を含んでいてもよい。

In the general formula (3), R ⁷ , R ⁸ and R ⁹ are each independently a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.

  The organic residue in the general formula (3) is, for example, an alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, or a propyl group, and an organic residue having 1 to 20 carbon atoms such as an ethenyl group or a propenyl group. An aromatic hydrocarbon group having 1 to 20 carbon atoms, such as a saturated aliphatic hydrocarbon group, a phenyl group, or a naphthyl group, and the alkyl group, the unsaturated aliphatic hydrocarbon group, and the aromatic hydrocarbon group are One or more hydrogen atoms may be substituted with at least one group selected from a hydroxyl group, a carboxyl group, an ether group, and an ester group.

  Although the content rate of the said ring structure except the lactone ring structure in an acrylic resin (A) is not specifically limited, For example, it is 5-90 mass%, Preferably it is 10-70 mass%, More preferably, this is 10-60 mass %, More preferably 10 to 50%.

  When the acrylic resin (A) has a lactone ring structure in the main chain, the content of the lactone ring structure in the resin is not particularly limited, but is, for example, 5 to 90% by mass, preferably 10 to 80% by mass. More preferably, it is 10-70 mass%, More preferably, it is 20-60 mass%.

  When the content of the ring structure in the acrylic resin (A) becomes transiently small, the heat resistance of the film may be lowered, and the solvent resistance and surface hardness may be insufficient. On the other hand, when the above content rate increases transiently, the moldability and mechanical properties of the film deteriorate.

  The acrylic resin (A) having a ring structure in the main chain can be produced by a known method. An acrylic resin whose ring structure is a glutaric anhydride structure or a glutarimide structure can be produced, for example, by the method described in WO2007 / 26659 or WO2005 / 108438. An acrylic resin whose ring structure is a maleic anhydride structure or an N-substituted maleimide structure can be produced, for example, by the method described in JP-A-57-153008 and JP-A-2007-31537. An acrylic resin whose ring structure is a lactone ring structure can be produced by, for example, the method described in JP-A-2006-96960, JP-A-2006-171464, or JP-A-2007-63541.

  The acrylic resin (A) may have a structural unit other than the (meth) acrylic acid ester unit and the (meth) acrylic acid unit. Examples of such a structural unit include styrene, vinyltoluene, and α-methyl. Styrene, α-hydroxymethylstyrene, α-hydroxyethylstyrene, acrylonitrile, methacrylonitrile, methallyl alcohol, allyl alcohol, ethylene, propylene, 4-methyl-1-pentene, vinyl acetate, 2-hydroxymethyl-1-butene , A structural unit derived from monomers such as methyl vinyl ketone, N-vinyl pyrrolidone and N-vinyl carbazole. The acrylic resin (A) may have two or more of these structural units.

  The acrylic resin (A) may have a structural unit having an effect of giving negative intrinsic birefringence to the resin. In this case, the degree of freedom in controlling the birefringence in the film made of the acrylic resin (A) is improved, and the use application of the optical film in the present invention is expanded.

  Intrinsic birefringence refers to the orientation axis from the refractive index n1 of light in a direction parallel to the direction (orientation axis) in which molecular chains are oriented in a layer (for example, a sheet or film) in which resin molecular chains are uniaxially oriented. A value obtained by subtracting the refractive index n2 of the light in the direction perpendicular to (i.e., "n1-n2"). The positive / negative of the intrinsic birefringence of the acrylic resin (A) itself is determined by the balance between the action of the structural unit with respect to the intrinsic birefringence and the action of the other structural unit of the acrylic resin (A).

  An example of a structural unit having an effect of giving negative intrinsic birefringence to the acrylic resin (A) is a styrene unit.

  The weight average molecular weight of an acrylic resin (A) is the range of 1000-500000, for example, Preferably it is the range of 5000-300000, More preferably, it is the range of 10,000-250,000, More preferably, it is the range of 50000-200000. is there.

  The acrylic resin (A) may have an ultraviolet absorbing ability as long as the heat resistance, physical properties, and optical properties are not impaired. Specifically, a method using an ultraviolet-absorbing monomer and / or an ultraviolet-stable monomer as a monomer component when producing the acrylic resin (A), an ultraviolet absorber and / or an ultraviolet stabilizer There exists a method of mix | blending with the said acrylic resin (A). Moreover, as long as there is no trouble in the optical film containing an acrylic resin (A), you may use these methods together. In order to maintain the ultraviolet absorbing function, it is preferable to use an ultraviolet absorbing monomer and an ultraviolet stabilizing monomer in combination, or to use an ultraviolet absorber and an ultraviolet stabilizer in combination. It is also preferable to use an ultraviolet absorber and / or an ultraviolet stabilizer in combination with the ultraviolet absorbing monomer and / or the ultraviolet stabilizing monomer.

  Examples of the ultraviolet absorbing monomer include benzotriazole compounds, benzophenone compounds or triazine compounds and acrylic monomers having a polymerizable unsaturated group. Examples of benzotriazole compounds include 2- [2′-hydroxy-5 ′-(meth) acryloyloxymethylphenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-(meth) acryloyloxyethyl. Phenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-(meth) acryloyloxypropylphenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-(meth) acryloyloxyhexyl Phenyl] -2H-benzotriazole, 2- [2′-hydroxy-3′-tert-butyl-5 ′-(meth) acryloyloxyethylphenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′ -(Β- (Meth) acryloyloxyethoxy) -3′-tert-butyl Enyl] -5-tert-butyl-2H-benzotriazole, 2- [2′-hydroxy-3′-methacrylaminomethyl-5 ′-(1 ″, 1 ″, 3 ″, 3 ″ -tetramethyl) butylphenyl ] -2H-benzotriazole and the like can be used. Examples of the benzophenone compounds include 2-hydroxy-4- [2- (meth) acryloyloxy] ethoxybenzophenone, 2-hydroxy-4- [2- (meth) acryloyloxy] butoxybenzophenone, 2,2 ′. -Dihydroxy-4- [2- (meth) acryloyloxy] ethoxybenzophenone, 2-hydroxy-4- [2- (meth) acryloyloxy] ethoxy-4 '-(2-hydroxyethoxy) benzophenone, and the like can be used. . Examples of the triazine compound include 4-diphenyl-6- [2-hydroxy-4- (2-acryloyloxyethoxy)]-s-triazine, 2,4-bis (2-methylphenyl) -6- [2-Hydroxy-4- (2-acryloyloxyethoxy)]-s-triazine, 2,4-bis (2-methoxyphenyl) -6- [2-hydroxy-4- (2-acryloyloxyethoxy)]- An s-triazine or the like can be used. When using such an ultraviolet-absorbing monomer, it is preferably copolymerized in an amount of 0.1 to 25% by weight, more preferably 1 to 15% by weight of all monomers. . If the content is small, the contribution to improving the weather resistance is low, and if the content is too large, the hot water resistance and solvent resistance may decrease or yellowing may occur.

  As the UV-stable monomer, a monomer having a polymerizable unsaturated group bonded to a hindered amine compound can be used, and specific examples include 4- (meth) acryloyloxy-2,2,6,6. -Tetramethylpiperidine, 4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- ( (Meth) acryloylamino-1,2,2,6,6-pentamethylpiperidine, 4-cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2 , 2,6,6-tetramethylpiperidine, 4-crotonoylamino-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4- (me ) Acryloylamino-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4-cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl -4-crotonoyloxy-2,2,6,6-tetramethylpiperidine and the like. When such an ultraviolet-stable monomer is used, it is preferably copolymerized in an amount of 0.1 to 25% by weight, more preferably 1 to 15% by weight of all monomers. . If the content is small, the contribution to improving the weather resistance is low, and if the content is too large, the hot water resistance and solvent resistance may decrease or yellowing may occur.

  Examples of the ultraviolet absorber include benzophenone compounds, salicinate compounds, benzoate compounds, triazole compounds, and triazine compounds. Examples of the benzophenone compounds include 2,4-dihydroxybenzophenone, 4-n-octyloxy-2-hydroxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2-hydroxy-4-n-octyl. Examples thereof include oxybenzophenone, bis (5-benzoyl-4-hydroxy-2-methoxyphenyl) methane, 1,4-bis (4-benzoyl-3-hydroxyphenone) -butane and the like. Examples of the silicate compound include pt-butylphenyl silicate. Examples of the benzoate compound include 2,4-di-t-butylphenyl-3 ', 5'-di-t-butyl-4'-hydroxybenzoate. Examples of triazole compounds include 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (3 , 5-Di-tert-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -p-cresol, 2- (2H-benzotriazol-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol, 2-benzotriazol-2-yl-4,6-di-tert-butylphenol, 2- [5-chloro (2H) -benzotriazole- 2-yl] -4-methyl-6-tert-butylphenol, 2- (2H-benzotriazol-2-yl) -4,6-di-tert-butylphenol, 2- 2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol, 2- (2H-benzotriazol-2-yl) -4-methyl-6- (3,4) , 5,6-tetrahydrophthalimidylmethyl) phenol, methyl 3- (3- (2H-benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl) propionate / polyethylene glycol 300 reaction product 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2- Hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 3- (2H-benzotriazol-2-yl ) -5- (1,1-dimethylethyl) -4-hydroxy -C7-9 side chain and straight chain alkyl esters. Furthermore, as triazine compounds, 2-mono (hydroxyphenyl) -1,3,5-triazine compounds, 2,4-bis (hydroxyphenyl) -1,3,5-triazine compounds, 2,4,6- And tris (hydroxyphenyl) -1,3,5-triazine compounds, specifically, 2,4-diphenyl-6- (2-hydroxy-4-methoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-ethoxyphenyl) -1,3,5-triazine, 2,4-diphenyl- (2-hydroxy-4-propoxyphenyl) -1,3,5- Triazine, 2,4-diphenyl- (2-hydroxy-4-butoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-butoxy) Enyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-hexyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2- Hydroxy-4-octyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-dodecyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl -6- (2-hydroxy-4-benzyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-butoxyethoxy) -1,3,5-triazine, 2,4-bis (2-hydroxy-4-butoxyphenyl) -6- (2,4-dibutoxyphenyl) -1,3-5-triazine, 2,4,6-tris (2-hydroxy-4- Me Xylphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-4-ethoxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-4) -Propoxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-4-butoxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy) -4-butoxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-4-hexyloxyphenyl) -1,3,5-triazine, 2,4,6-tris ( 2-hydroxy-4-octyloxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-4-dodecyloxyphenyl) -1,3,5-triazine, 2,4 6-Tris (2-hydroxy-4-benzyloxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-4-ethoxyethoxyphenyl) -1,3,5-triazine, 2,4 , 6-Tris (2-hydroxy-4-butoxyethoxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-4-propoxyethoxyphenyl) -1,3,5-triazine 2,4,6-tris (2-hydroxy-4-methoxycarbonylpropyloxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-4-ethoxycarbonylethyloxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-4- (1- (2-ethoxyhexyloxy) -1-oxopropane-2- Ruoxy) phenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-3-methyl-4-methoxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-3-methyl-4-ethoxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-3-methyl-4-propoxyphenyl) -1,3,5 Triazine, 2,4,6-tris (2-hydroxy-3-methyl-4-butoxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-3-methyl-4) -Butoxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-3-methyl-4-hexyloxyphenyl) -1,3,5-triazine, 2,4,6- Tris (2-hydroxy 3-methyl-4-octyloxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-3-methyl-4-dodecyloxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-3-methyl-4-benzyloxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-3-methyl-4-ethoxy) Ethoxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-3-methyl-4-butoxyethoxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-3-methyl-4-propoxyethoxyphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-3-methyl-4-methoxycarbonylpropyloxy) Ciphenyl) -1,3,5-triazine, 2,4,6-tris (2-hydroxy-3-methyl-4-ethoxycarbonylethyloxyphenyl) -1,3,5-triazine, 2,4,6- And tris (2-hydroxy-3-methyl-4- (1- (2-ethoxyhexyloxy) -1-oxopropan-2-yloxy) phenyl) -1,3,5-triazine. Among them, 2,4-bis (2,4-dimethylphenyl) -6- [2-hydroxy-4 is preferred because it is highly compatible with amorphous thermoplastic resins, particularly acrylic resins, and has excellent absorption characteristics. UV absorbers having-(3-alkyloxy-2-hydroxypropyloxy) -5-α-cumylphenyl] -s-triazine skeleton (alkyloxy; long-chain alkyloxy groups such as octyloxy, nonyloxy, decyloxy, etc.) It is done. Further, an ultraviolet absorber having a 2,4,6-tris (hydroxyphenyl) -1,3,5-triazine skeleton is preferably used, and 2,4,6-tris (2-hydroxy-4-long chain alkyloxy) is used. Group-substituted phenyl) -1,3,5-triazine skeleton and 2,4,6-tris (2-hydroxy-3-alkyl-4-long-chain alkyloxy group-substituted phenyl) -1,3,5-triazine skeleton The ultraviolet absorber having is a particularly preferred triazine-based ultraviolet absorber. Examples of commercially available products include “Tinuvin 1577”, “Tinuvin 460” and “Tinuvin 477” (manufactured by Ciba Japan) as triazine-based UV absorbers, and “Adeka Stub LA-31” (manufactured by ADEKA) as triazole-based UV absorbers. It is done.

  These can be used alone or in combination of two or more. Moreover, it is also preferable to use together the method of copolymerizing the said ultraviolet absorptive monomer with an ultraviolet absorber. Although the compounding quantity of a ultraviolet-stable monomer ultraviolet absorber is not specifically limited, It is preferable that it is 0.01-25 mass% in the film containing an amorphous thermoplastic resin, More preferably, it is 0.05- 10% by mass. If the amount added is too small, the contribution to improving weather resistance is low, and if it is too large, the mechanical strength may be lowered or yellowing may be caused.

  The acrylic resin (A) may contain other resins as long as the effects of the present invention are not impaired. The content of other resins is preferably 0 to 50% by mass, more preferably 0 to 25% by mass, and still more preferably 0 to 10% by mass.

  Examples of other resin components include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly (4-methyl-1-pentene); halogen-containing polymers such as vinyl chloride and chlorinated vinyl resins; Acrylic polymers such as polymethyl methacrylate; styrene polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer; polyethylene terephthalate, polybutylene terephthalate, Polyesters such as polyethylene naphthalate; biodegradable polyesters such as polylactic acid and polybutylene succinate; cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate Cellulose polymers such as nylon; polyamides such as nylon 6, nylon 66, nylon 610; polyacetal; polyphenylene oxide; polyphenylene sulfide; polyether ether ketone; polyether nitrile; polysulfone; And rubber polymers such as ABS resin and ASA resin blended with polybutadiene rubber and acrylic rubber; From the viewpoint of compatibility, a styrene-acrylonitrile copolymer is preferable. The rubbery polymer preferably has a graft portion having a composition compatible with the acrylic resin (A) on the surface, and the average particle diameter of the rubbery polymer is from the viewpoint of improving transparency when formed into a film. Therefore, it is preferably 400 nm or less, more preferably 200 nm or less, still more preferably 100 nm or less, and particularly preferably 70 nm or less.

  The acrylic resin (A) may contain other additives. The content of other additives in the acrylic resin (A) is preferably 0 to 5% by mass, more preferably 0 to 2% by mass, and still more preferably 0 to 0.5% by mass. Examples of other additives include hindered phenol-based, phosphorus-based and sulfur-based antioxidants; light-resistant stabilizers, weather-resistant stabilizers, heat-stabilizers, and other stabilizers; reinforcing materials such as glass fibers and carbon fibers. Near infrared absorbers; flame retardants such as tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide; antistatic agents such as anionic, cationic and nonionic surfactants; inorganic pigments, organic pigments, dyes, etc. Colorants; organic fillers and inorganic fillers; resin modifiers; plasticizers; lubricants.

  A known antioxidant can be used as the antioxidant. Examples of phenolic antioxidants include n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, n-octadecyl-3- (3,5-di-t-butyl). -4-hydroxyphenyl) acetate, n-octadecyl-3,5-di-t-butyl-4-hydroxybenzoate, n-hexyl-3,5-di-t-butyl-4-hydroxyphenylbenzoate, n-dodecyl 3,5-di-t-butyl-4-hydroxyphenylbenzoate, neododecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, dodecyl-β- (3,5-di- t-butyl-4-hydroxyphenyl) propionate, ethyl-α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate Octadecyl-α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octadecyl-α- (4-hydroxy-3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2- (n-octylthio) ethyl-3,5-di-t-butyl-4-hydroxybenzoate, 2- (n-octylthio) ethyl-3,5-di-t-butyl-4-hydroxyphenyl acetate, 2 -(N-octadecylthio) ethyl-3,5-di-t-butyl-4-hydroxyphenyl acetate, 2- (n-octadecylthio) ethyl-3,5-di-t-butyl-4-hydroxybenzoate, 2- (2-hydroxyethylthio) ethyl-3,5-di-t-butyl-4-hydroxybenzoate, diethyl glycol bis- (3,5 -Di-t-butyl-4-hydroxy-phenyl) propionate, 2- (n-octadecylthio) ethyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, stearamide-N, N -Bis- [ethylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], n-butylimino-N, N-bis- [ethylene-3- (3,5-di-t -Butyl-4-hydroxyphenyl) propionate], 2- (2-stearoyloxyethylthio) ethyl-3,5-di-t-butyl-4-hydroxybenzoate, 2- (2-stearoyloxyethylthio) ethyl- 7- (3-Methyl-5-tert-butyl-4-hydroxyphenyl) heptanoate, 1,2-propylene glycol bis- [3- (3,5 Di-t-butyl-4-hydroxyphenyl) propionate], ethylene glycol bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], neopentyl glycol bis- [3- (3 , 5-di-t-butyl-4-hydroxyphenyl) propionate], ethylene glycol bis- (3,5-di-t-butyl-4-hydroxyphenyl acetate), glycerin-1-n-octadecanoate- 2,3-bis- (3,5-di-t-butyl-4-hydroxyphenyl acetate), pentaerythritol tetrakis- [3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) Propionate], 1,1,1-trimethylolethanetris- [3- (3,5-di-tert-butyl-4-hydroxypheny ) Propionate], sorbitol hexa- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl-7- (3-methyl-5-tert-butyl-4-hydroxy Phenyl) propionate, 2-stearoyloxyethyl-7- (3-methyl-5-tert-butyl-4-hydroxyphenyl) heptanoate, 1,6-n-hexanediol bis-[(3 ', 5'-di- t-butyl-4-hydroxyphenyl) propionate], pentaerythritol tetrakis- (3,5-di-t-butyl-4-hydroxyhydrocinnamate), 3,9-bis [1,1-dimethyl-2- [ [beta]-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] 2,4,8,10-tetrao Saspiro [5,5] -undecane, 2,4-di-t-amyl-6- [1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl] phenyl acrylate and 2-t-butyl -6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate.

  Examples of the thioether-based antioxidant include pentaerythrityl tetrakis (3-laurylthiopropionate), dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl. -3,3'-thiodipropionate.

  Examples of phosphorus antioxidants include tris (2,4-di-t-butylphenyl) phosphite, 2-[[2,4,8,10-tetrakis (1,1-dimethylethyl) dibenzo [d. , F] [1,3,2] dioxaphosphin-6-yl] oxy] -N, N-bis [2-[[2,4,8,10-tetrakis (1,1 dimethylethyl) dibenzo [D, f] [1,3,2] dioxaphosphin-6-yl] oxy] -ethyl] ethanamine, diphenyltridecyl phosphite, triphenyl phosphite, 2,2-methylenebis (4,6- Di-t-butylphenyl) octyl phosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, distearyl pentaerythritol diphosphite DOO, cyclic neopentanetetraylbis (2,6-di -t- butyl-4-methylphenyl) phosphite and the like.

[Amorphous ester polymer (B)]
The amorphous ester polymer (B) of the present invention has a GPC weight average molecular weight of 500 to 5000 in terms of polystyrene, and is not particularly limited except that it is amorphous.

  The weight average molecular weight of GPC in terms of polystyrene is 500 to 5000, more preferably 700 to 4000, and still more preferably 1000 to 3000. When the molecular weight is 500 or less, bleeding out is likely to occur during molding, and appearance or optical defects are likely to occur. Moreover, when molecular weight is 5000 or more, compatibility with an acrylic resin (A) falls and the use for an optical use may become difficult.

  The amorphous ester polymer (B) of the present invention is an amorphous polymer that does not exhibit a melting point in the temperature range of 0 ° C to 300 ° C. Since it is amorphous, it is excellent in compatibility with the acrylic resin (A).

  The amorphous ester polymer (B) of the present invention preferably has an aromatic ring structure. Aromatic ring structures include monocyclic structures such as benzene, pyridine, pyrrole, furan, and thiophene rings, as well as condensed ring structures such as naphthalene, anthracene, benzimidazole, fluorene, and carbazole rings. Can be mentioned. When the amorphous ester polymer (B) has an aromatic ring structure, the stress optical coefficient (Cr) can be improved, which is suitable when the optical film of the present invention is used as a retardation film.

  Here, the stress optical coefficient (Cr) is an amount indicating the magnitude of birefringence with respect to stress in a rubber state, and when an optically isotropic substance is oriented by applying external force in a rubber state, Anisotropy occurs, causing birefringence. The intrinsic birefringence Δn (= n1−n2), which is the difference between the two refractive indexes n1 and n2, which is a measure of birefringence, is divided by the stress σ corresponding to this strain, that is, Δn / σ.

  The amorphous ester polymer (B) of the present invention preferably has an alicyclic structure. The alicyclic structure includes cyclobutane ring, cyclobutene ring, cyclopentane ring, cyclopentene ring, cyclopentadiene ring, cyclohexane ring, cyclohexene ring, cycloheptane, cyclooctane ring, decalin ring and other aliphatic rings, norbornene ring, adamantane ring, etc. Of the spiro ring structure. When the amorphous ester polymer (B) has an alicyclic structure, compatibility with the acrylic resin (A) is improved, and bleeding out during molding can be suppressed.

  The diol unit constituting the amorphous ester polymer (B) of the present invention is not particularly limited, but ethylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6 -Aliphatic diols such as hexanediol, diethylene glycol, propylene glycol, neopentyl glycol; polyether compounds such as polyethylene glycol, polypropylene glycol, polybutylene glycol; 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol 1,2-decahydronaphthalene diethanol, 1,3-decahydronaphthalene diethanol, 1,4-decahydronaphthalene diethanol, 1,5-decahydronaphthalene diethanol, 1,6-decahydronaphthalene diethanol Alicyclic hydrocarbon diols such as diol, 2,7-decahydronaphthalene diethanol, tetralin dimethanol, norbornane dimethanol, tricyclodecane dimethanol, pentacyclododecane dimethanol; 4,4 ′-(1-methyl Bisphenols such as ethylidene) bisphenol, methylene bisphenol (bisphenol F), 4,4′-cyclohexylidene bisphenol (bisphenol Z), 4,4′-sulfonylbisphenol (bisphenol S); alkylene oxide adducts of the bisphenols; Aromatic dihydroxy compounds such as hydroquinone, resorcin, 4,4′-dihydroxybiphenyl, 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenylbenzophenone; Diol units derived from alkylene oxide adducts of dihydroxy compounds can be exemplified.

  On the other hand, the dicarboxylic acid unit is not particularly limited, but succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, cyclohexanedicarboxylic acid, norbornane dicarboxylic acid , Aliphatic dicarboxylic acids such as tricyclodecane dicarboxylic acid and pentacyclododecane dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 2-methyl terephthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, Examples include dicarboxylic acid units derived from dicarboxylic acids such as aromatic dicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and tetralindicarboxylic acid.

  In addition, the amorphous ester polymer (B) of the present invention is a monoalcohol unit such as butyl alcohol, hexyl alcohol, octyl alcohol or the like, trimethylolpropane, glycerin, pentaerythritol and the like within a range not impairing the object of the present invention. It is also possible to introduce polyhydric alcohol units having higher valences, monocarboxylic acid units such as benzoic acid, propionic acid and butyric acid, and trivalent or higher polyvalent carboxylic acid units such as trimellitic acid, trimesic acid and pyromellitic acid.

  There is no restriction | limiting in particular in the method of manufacturing the amorphous ester polymer (B) of this invention, A conventionally well-known method is applicable. Examples thereof include a melt polymerization method such as a transesterification method and a direct esterification method, a solution polymerization method, and a solid phase polymerization method.

[Acrylic resin composition]
The acrylic resin composition of the present invention comprises a composition containing 90 to 99.5 parts by mass of the acrylic resin (A) and 0.5 to 10 parts by mass of the amorphous ester polymer (B).

  The content of the amorphous ester polymer (B) in the acrylic resin composition of the present invention is 0. When the total of the acrylic resin (A) and the amorphous ester polymer (B) is 100 parts by mass. It is 5-10 mass parts, and 1-5 mass parts is more preferable. If it is 0.5 parts by mass or less, the phase difference characteristics may be insufficient. On the other hand, if the amount exceeds 10 parts by mass, the compatibility may be insufficient, Tg may be significantly reduced, or the mechanical strength may be lowered or yellowed.

  Tg of the acrylic resin composition is preferably 110 ° C or higher, more preferably 115 ° C or higher, further preferably 120 ° C or higher, and particularly preferably 130 ° C or higher.

  The acrylic resin composition preferably has a total light transmittance of 80% or more measured according to JIS K7361-1, more preferably 85% or more, still more preferably 90% or more, and particularly preferably 92% or more. It is.

  If the acrylic resin (A) has a ring structure and the Tg of the resin composition is increased, the molding temperature of the composition needs to be increased. When the molding temperature becomes high, foaming and bleed out of the additive are likely to occur during molding, and the transpiration of the additive tends to increase. However, in the acrylic resin composition of the present invention, even in such a case, the occurrence of foaming and bleeding out is small, and the occurrence of problems due to the transpiration of the additive can be suppressed.

[Optical film]
The optical film of the present invention comprises the above acrylic resin composition. The optical film of the present invention has high heat resistance and transparency. For example, the optical film of the present invention has few defects such as foaming and bleeding out. For example, the optical film of the present invention is excellent in flexibility. Due to these characteristics, the optical film of the present invention can be suitably used as an optical member of a liquid crystal display device. Further, due to the high heat resistance, it can be placed close to a heat generating part such as a light source.

  The thickness of the optical film of the present invention is, for example, 1 μm or more and less than 1000 μm, preferably 10 μm or more and less than 350 μm, more preferably 20 μm or more and less than 250 μm. When the thickness is less than 1 μm, the strength as an optical film may be insufficient, and breakage or the like is likely to occur during post-processing such as stretching.

  The optical film of the present invention has a high Tg, for example, a value of 110 ° C. or higher. Depending on the composition of the resin composition constituting the optical film, Tg is 115 ° C. or higher, 120 ° C. or higher, and further 130 ° C. or higher.

  The optical film of the present invention is less colored, and the b value per 250 μm thickness is preferably 0.5 or less, more preferably 0.3 or less.

  In the optical film of the present invention, the haze measured according to JIS K7136 is preferably 5% or less, more preferably 3% or less. If the haze exceeds 5%, the transmittance is lowered and may not be suitable for optical applications.

  The optical film of the present invention has a high light transmittance. The total light transmittance measured according to JIS K7361-1 is preferably 80% or more, more preferably 85% or more, still more preferably 90% or more, and particularly preferably 92% or more.

The stress optical coefficient (Cr) of the optical film of the present invention is preferably 0.30 × 10 ⁻⁹ Pa ⁻¹ or more. When Cr is less than 0.30 × 10 ⁻⁹ Pa ⁻¹ , the stress for inducing the required birefringence increases, which is not preferable because the film is easily broken. Although there is no restriction | limiting in particular in an upper limit, Usually, it is 6.50 * 10 <^-9> Pa <^-1> or less.

  In the optical film of the present invention, the stress optical coefficient is improved by the amorphous ester polymer (B). When compared with the stress optical coefficient of the optical film not containing the amorphous ester polymer (B) in the acrylic resin composition, the content of the amorphous ester polymer (B) relative to 1% by mass of the acrylic resin composition The increase rate of the stress optical coefficient (Cr increase rate) is preferably 0.5% or more, more preferably 1% or more, and further preferably 2% or more. The upper limit is not particularly limited, but is usually 100% or less. If the rate of increase is 0.5% or less, it is necessary to increase the content in order to exhibit a sufficient effect, and there is a possibility that the Tg will be lowered or the compatibility will be insufficient. On the other hand, when the rate of increase is too large, there is a risk that uneven retardation is likely to occur when a retardation film is formed.

  The optical film of the present invention may be a stretched film. The type of stretching is not particularly limited, and may be uniaxial stretching or biaxial stretching. By stretching, the mechanical strength of the optical film can be improved, and it can function as a retardation film by imparting birefringence to the optical film.

  The optical film of the present invention may be a retardation film. The in-plane retardation Re for light having a wavelength of 589 nm as the retardation film is, for example, 20 to 1000 nm, preferably 30 to 600 nm, more preferably 30 to 350 nm, and further preferably 50 to 200 nm. The thickness direction retardation Rth is, for example, 20 to 1000 nm, preferably 30 to 600 nm, more preferably 30 to 400 nm, and further preferably 50 to 300 nm.

  Here, the in-plane retardation Re and the thickness direction retardation Rth are the refractive index in the slow axis direction (direction showing the maximum refractive index in the film plane) in the plane of the film measured at a wavelength of 589 nm. nx, the refractive index in the fast axis direction in the plane of the film (direction perpendicular to nx in the film plane) is ny, the refractive index in the thickness direction of the film is nz, and the thickness of the film is d (nm). Sometimes, the value is represented by the equation Re = (nx−ny) × d and the equation Rth = {(nx + ny) / 2−nz} × d.

  The optical film of the present invention is preferably a retardation film satisfying Re (447) / Re (590) <1. At this time, Re (447) and Re (590) are in-plane retardations of the optical film measured at measurement light wavelengths of 447 nm and 590 nm, respectively. The fact that the phase difference becomes smaller as the wavelength is shorter is called “reverse wavelength dispersion”. In the optical film of the present invention, the acrylic resin (A) having a ring structure in the main chain has a heteroaromatic unit in the side chain. Reverse wavelength dispersibility can be exhibited by copolymerizing monomer units or forming a composition with a copolymer having a heteroaromatic unit in the side chain. As such a heteroaromatic unit, a vinylcarbazole unit is preferable.

  In the retardation film of the present invention, when Re (447) / Re (590) <1, Re (447) / Re (590) is preferably 0.70 to 0.99, more preferably 0. .75 to 0.96, more preferably 0.80 to 0.93.

  Various functional coating layers may be formed on the surface of the optical film of the present invention as necessary. Functional coating layers include, for example, antistatic layers, adhesive layers, adhesive layers, easy adhesion layers, antiglare (non-glare) layers, antifouling layers such as photocatalyst layers, antireflection layers, hard coat layers, and UV shielding layers. Layers, heat ray shielding layers, electromagnetic wave shielding layers, gas barrier layers, and the like. Moreover, the member which has the said functional coating layer may be laminated | stacked on the optical film of this invention. Lamination of the member can be performed via an adhesive or an adhesive.

  Although the use of the optical film of the present invention is not particularly limited, it can be suitably used as an optical member due to its high transparency and heat resistance. The optical member is, for example, an optical protective film, specifically, a protective film for various optical disk (VD, CD, DVD, MD, LD, etc.) substrates, and a polarized light included in an image display device such as a liquid crystal display (LCD). It is a polarizer protective film used for a board. As an optical film such as retardation film, λ / 4 plate, λ / 2 plate, viewing angle compensation film, light diffusion film, reflection film, antireflection film, antiglare film, brightness enhancement film, conductive film for touch panel, etc. The optical film may be used. In particular, the optical film of the present invention is suitable as an optical compensation member for LCD. For example, suitable for retardation films of various LCDs such as STN type LCD, TFT-TN type LCD, OCB type LCD, VA type LCD, IPS type LCD, optical compensation film, laminated film with polarizing plate, polarizing optical compensation film Can be used for The preferable optical characteristics of the retardation film comprising the optical film of the present invention vary depending on the display mode of the liquid crystal used.

[Method for producing optical film]
The method for forming the optical film of the present invention is not particularly limited, and for example, a known technique such as cast molding, melt extrusion molding, press molding or the like may be used.

  As a method for producing the optical film of the present invention, there is an extrusion molding method. As a specific example, after each component constituting the resin composition is pre-blended with a mixer such as an omni mixer, the resulting mixture may be extrusion kneaded from a kneader. The kneader used for the extrusion kneading is not particularly limited, and for example, a known kneader such as a single screw extruder, a twin screw extruder, or a pressure kneader can be used.

  Alternatively, a separately formed resin composition may be melt-extruded. Examples of the melt extrusion method include a T-die method and an inflation method, and the molding temperature at that time is preferably 200 to 350 ° C., more preferably 250 to 300 ° C., further preferably 255 to 300 ° C., particularly Preferably it is 260 to 300 degreeC.

  When the T-die method is used, an optical film wound into a roll can be obtained by attaching a T-die to the tip of the extruder and winding the film extruded from the T-die. At this time, it is also possible to control the temperature and speed of winding and to stretch (uniaxial stretching) in the extrusion direction of the film. Further, the film may be stretched in a direction perpendicular to the extrusion direction, and sequential biaxial stretching or simultaneous biaxial stretching may be performed.

  When an extruder is used for extrusion molding, the type is not particularly limited and may be uniaxial, biaxial, or multiaxial, but its L / D value is (L is the value of the extruder) Cylinder length, D is cylinder inner diameter), in order to sufficiently plasticize the resin composition to obtain a good kneaded state, it is preferably 10 or more and 100 or less, more preferably 15 or more and 80 or less, and still more preferably Is 20 or more and 60 or less. When the L / D value is less than 10, the resin composition cannot be sufficiently plasticized and a good kneaded state may not be obtained. On the other hand, if the L / D value exceeds 100, the resin in the composition may be thermally decomposed due to excessive generation of shear heat to the resin composition.

  In this case, the set temperature of the cylinder is preferably 200 ° C. or higher and 350 ° C. or lower, more preferably 250 ° C. or higher and 300 ° C. or lower. If setting temperature is less than 200 degreeC, the melt viscosity of a resin composition will become high too much, and the productivity of an optical film will fall. On the other hand, if the set temperature exceeds 350 ° C., the resin in the resin composition may be thermally decomposed.

  When an extruder is used for extrusion molding, the shape is not particularly limited, but the extruder preferably has one or more open vent portions. By using such an extruder, the decomposition gas can be sucked from the open vent portion, and the amount of volatile components remaining in the obtained optical film can be reduced. In order to suck the decomposition gas from the open vent portion, for example, the open vent portion may be in a reduced pressure state, and the degree of pressure reduction is preferably in the range of 931 to 1.3 hPa as the pressure of the open vent portion, 798 A range of ˜13.3 hPa is more preferable. When the pressure in the open vent portion is higher than 931 hPa, volatile components or monomer components generated by decomposition of the resin tend to remain in the resin composition. On the other hand, it is industrially difficult to keep the pressure of the open vent part lower than 1.3 hPa.

  When producing the optical film of the present invention, it is preferable to incorporate a filtration step such as filtration with a polymer filter. By incorporating the filtration step, foreign substances present in the resin composition can be removed, so that defects in the appearance of the obtained film can be reduced. In addition, at the time of filtration with a polymer filter, a resin composition will be in a high temperature molten state. For this reason, the resin composition deteriorates when passing through the polymer filter, gas components and colored deterioration products formed by the deterioration flow into the composition, and the resulting film has holes, flow patterns, and flows. Defects such as streaks may be observed. This defect is easily observed especially during continuous molding of optical films. For this reason, when molding a resin composition filtered through a polymer filter, the molding temperature decreases the melt viscosity of the resin composition and shortens the residence time of the resin composition in the polymer filter, for example, 255. It is -350 degreeC and 260-320 degreeC is preferable.

  The configuration of the polymer filter is not particularly limited, but a polymer filter in which a large number of leaf disk filters are arranged in a housing can be suitably used. The filter material of the leaf disk type filter may be any of a type in which a metal fiber nonwoven fabric is sintered, a type in which metal powder is sintered, a type in which several metal meshes are laminated, or a hybrid type in which they are combined. The sintered type is most preferred.

  The filtration accuracy by the polymer filter is not particularly limited, but is usually 15 μm or less, preferably 10 μm or less, more preferably 5 μm or less. When the filtration accuracy is 1 μm or less, the residence time of the resin composition becomes longer, so that the thermal deterioration of the composition increases, and the productivity of the optical film decreases. On the other hand, when the filtration accuracy exceeds 15 μm, it is difficult to remove foreign substances in the resin composition.

The filtration area with respect to the resin treatment amount per hour in the polymer filter is not particularly limited, and can be appropriately set according to the treatment amount of the resin composition. The filtration area is, for example, 0.001 to 0.15 m ² / (kg / hour).

  The shape of the polymer filter is not particularly limited. For example, an inner flow type having a plurality of resin flow ports and a resin flow path in the center pole; the inner peripheral surface of the leaf disk filter at a plurality of vertices or faces And an external flow type having a resin flow path on the outer surface of the center pole. In particular, it is preferable to use an external flow type in which the resin stays are small.

  Although there is no restriction | limiting in particular in the residence time of the resin composition in a polymer filter, Preferably it is 20 minutes or less, More preferably, it is 10 minutes or less, More preferably, it is 5 minutes or less. Further, the filter inlet pressure and the filter outlet pressure during filtration are, for example, 3 to 15 MPa and 0.3 to 10 MPa, respectively, and the pressure loss (the pressure difference between the filter inlet pressure and the outlet pressure) is 1 MPa to 15 MPa. A range is preferred. When the pressure loss is 1 MPa or less, the resin composition tends to be biased in the flow path through the filter, and the quality of the obtained optical film tends to deteriorate. On the other hand, when the pressure loss exceeds 15 MPa, the polymer filter is easily damaged.

  What is necessary is just to set suitably the temperature of the resin composition introduce | transduced into a polymer filter according to the melt viscosity, for example, it is 250-300 degreeC, Preferably it is 255-300 degreeC, More preferably, it is 260-300 degreeC. is there.

  The specific process of obtaining an optical film with few foreign substances and colored substances by filtration using a polymer filter is not particularly limited. For example, (1) a process in which a resin composition is formed and filtered in a clean environment, and then the resin composition is molded in a clean environment; (2) a resin composition having foreign matters or colored substances is cleaned A process in which the resin composition is subsequently molded in a clean environment after being filtered in an environment; (3) a process in which a resin composition having a foreign substance or a colored product is simultaneously filtered and molded in a clean environment; Etc. You may perform the filtration process of the resin composition by a polymer filter in multiple times for each process.

  When filtering the resin composition with the polymer filter, it is preferable to install a gear pump between the extruder and the polymer filter to stabilize the pressure of the resin composition in the filter.

  The optical film obtained by extrusion may be stretched as necessary. The method of uniaxially or biaxially stretching the obtained optical film is not particularly limited, and a known method may be followed. Uniaxial stretching is typically free-end uniaxial stretching in which the change in the width direction of the film is free. Fixed-end uniaxial stretching is also possible in which the change in the width direction of the film is fixed. Biaxial stretching is typically sequential biaxial stretching, but simultaneous biaxial stretching in which longitudinal and transverse stretching are simultaneously performed can also be suitably used. Furthermore, it is also possible to stretch in the oblique direction with respect to stretching in the thickness direction or film roll. The stretching method, the stretching temperature, and the stretching ratio can be appropriately selected according to the target optical characteristics and mechanical characteristics.

  In order to stabilize the optical properties and mechanical properties of the optical film, heat treatment (annealing) may be performed as necessary after stretching.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the examples shown below. In the following description, for convenience, “part by mass” may be simply referred to as “part”, and “liter” may be simply referred to as “L”. For convenience, the following abbreviations are used in the examples.

TPA: dimethyl terephthalate EG: 1,2-ethanediol CHDM: 1,4-cyclohexanedimethanol MMA: methyl methacrylate MHMA: methyl 2- (hydroxymethyl) acrylate BMA: n-butyl methacrylate MA: acrylic acid Methyl NVCz: N-vinylcarbazole <weight average molecular weight>
The weight average molecular weight of the acrylic resin and the amorphous ester polymer was determined by gel permeation chromatography (GPC) under the following conditions.
System: GPC system HLC-8220 manufactured by Tosoh Corporation
Developing solvent: Chloroform (made by Wako Pure Chemical Industries, special grade), flow rate: 0.6 ml / min Standard sample: TSK standard polystyrene (manufactured by Tosoh Corporation, PS-oligomer kit)
Measurement side column configuration: guard column (manufactured by Tosoh Corp., TSKguardcolumn SuperHZ-L), separation column (manufactured by Tosoh Corp., TSKgel SuperHZM-M) 2 series connection reference side column configuration: reference column (manufactured by Tosoh Corp., TSKgel SuperH-RC) )
<Glass transition temperature>
The glass transition temperature (Tg) of each sample was determined in accordance with JIS K7121 regulations. Specifically, using a differential scanning calorimeter (manufactured by Rigaku, DSC-8230), a sample of about 10 mg was heated from a normal temperature to 200 ° C. at a heating rate of 20 ° C./min in a nitrogen gas atmosphere. It calculated by the starting point method from the DSC curve. Α-alumina was used as a reference.

<Melting point>
Using a differential scanning calorimeter (manufactured by Rigaku, DSC-8230), about 10 mg of a sample was melted and held at 280 ° C. for 5 minutes in a nitrogen gas atmosphere, and then rapidly cooled to 0 ° C. or lower with liquid nitrogen. The temperature at which an endothermic peak based on crystal melting was observed in the process of raising the temperature of this sample to 300 ° C. at a rate of 5 ° C./min was defined as the melting point.

<Haze of film>
The haze of the film was measured according to JIS K7136 using a turbidimeter (Nippon Denshoku Industries Co., Ltd., NDH-5000).

<Total light transmittance of film>
The total light transmittance of the film was measured according to JIS K7361-1 using the turbidimeter.

<Bleed-out>
In film production by extrusion molding, the film surface was visually confirmed and evaluated according to the following criteria.
○: No bleed out △: Slight bleed out is confirmed ×: Bleed out is remarkable <Filter filterability>
In the filtration step using a polymer filter, the filter filterability was evaluated according to the following criteria.
○: The pressure increase of the polymer filter is small and can be continuously produced. ×: The pressure increase of the polymer filter is remarkable.
The in-plane retardation Re of the optical film with respect to light having a wavelength of 589 nm was determined using a retardation measuring device (manufactured by Oji Scientific Instruments, KOBRA-WR). Specifically, the incident angle dependency (single N calculation) is selected as the measurement item, the average refractive index of the film measured with an Abbe refractometer, with the tilt axis as the slow axis and the incident angle as 40 °, The film thickness d was input and measured. The film thickness d of the optical film was measured using a Digimatic micrometer (manufactured by Mitutoyo).

  In the in-plane retardation Re of the optical film, nx is the refractive index in the slow axis direction (direction showing the maximum refractive index in the film plane) in the plane of the film, and ny is the fast axis direction in the plane of the film ( The refractive index in a direction perpendicular to nx in the film plane, d is a value represented by the formula Re = (nx−ny) × d, where the thickness of the film is (nm).

Re (447) and Re (590) represent in-plane retardations of incident light measured at 447 nm and 590 nm, respectively, and Re (447) / Re (590) was obtained from the obtained in-plane retardation values.
<Stress optical coefficient Cr of optical film>
The original films or unstretched optical films obtained in the production examples and examples were cut into 60 mm × 20 mm to obtain test pieces. A weight was attached to one of the short sides of the test piece so that an arbitrary stress of 1 MPa (N / mm ² ) or less was applied. Next, when the glass transition temperature of the original film is T0 ° C., the distance from the portion where the weight is attached is 40 mm in a constant temperature dryer (manufactured by ASONE, DOV-450A) maintained at (T0 + 3) ° C. Thus, the other short side of the test piece was fixed with a chuck, and the test piece was held for 30 minutes in a state in which the test piece was uniaxially stretched in the free direction by a load due to the weight. After 30 minutes, the heater of the dryer was turned off, and after allowing to cool under load until the temperature inside the dryer reached (T0-40) ° C., the film was taken out, and the length, thickness, The in-plane retardation for light having a wavelength of 589 nm and the mass of the weight used were measured. For each film, the weight mass was changed by changing 3 to 4 points. Next, the birefringence Δn of the film represented by Δn = nx−ny was obtained by dividing the measured in-plane retardation by the thickness of the film, and this was added to the y-axis and to the film. The stress σ (Pa) is obtained from the mass and the cross-sectional area of the weight, plotted on the x-axis, and the slope of the straight line of the plot is calculated by the least square method to obtain the stress optical coefficient Cr of the original film or the optical film. It was.
<Manufacture of acrylic resin>
(Production Example 1)
To a reaction kettle equipped with a stirrer, thermometer, cooler and nitrogen inlet tube, 33 parts of MMA, 17 parts of MHMA, 5.6 parts of BMA, 43 parts of toluene, 1.5 parts of methanol and 0.028 parts of Adeka Stub as an antioxidant 2112 (manufactured by ADEKA) was charged, and the temperature was raised to 88 ° C. through nitrogen, and 0.008 part of t-amylperoxy-2-ethylhexanoate (manufactured by Arkema Yoshitomi, product) Name: Lupazole 575) was added and 0.04 part of t-amylperoxy-2-ethylhexanoate dissolved in 0.8 part of toluene was added dropwise over 8 hours for 3 hours. Later, 23 parts of toluene was added dropwise over 4 hours, and the solution polymerization was allowed to proceed under reflux at about 95 to 100 ° C., and after completion of the addition, aging was further performed for 1 hour.

  Next, 0.1 part of stearyl phosphate (product name: Phoslex A-18, manufactured by Sakai Chemical Industry Co., Ltd.) is added to the polymer solution, and the cyclization condensation reaction proceeds for 2 hours under reflux at about 80 to 95 ° C. I let you.

Next, the polymer solution obtained by the cyclization condensation reaction was completed through a multi-tube heat exchanger heated to 240 ° C., and then the barrel temperature was 240 ° C., the rotation speed was 100 rpm, and the degree of vacuum was 13 .3-400 hPa, rear vent number 1 and fore vent number 4 (referred to as first, second, third and fourth vents from the upstream side) vent type screw twin screw extruder (L / D = 52.5 Was introduced at a treatment rate of 24 parts / hour in terms of the amount of resin and devolatilized. At that time, ion exchange water was injected at a rate of 0.4 part / hour after the first vent and the third vent. Further, separately prepared antioxidant and quencher mixed solution after the second vent was injected at a charging rate of 1.1 parts / hour. Antioxidants and deactivators are 0.6 parts of Irganox 1010 (manufactured by Ciba Specialty Chemicals), 0.6 parts of ADK STAB AO-412S (manufactured by ADEKA), zinc octylate (manufactured by Nippon Chemical Industry Co., Ltd., Nikka Octix zinc) 6%) was prepared by dissolving 4.2 parts of toluene in 94.7 parts. Through the above devolatilization process, the resin was cut and pelletized using a strand cutter to obtain an acrylic resin pellet (A-1) having a ring structure in the main chain. The weight average molecular weight was 145000. The obtained acrylic resin pellet was melt-pressed at 240 ° C. and 30 MPa for 5 minutes using a manual heating press machine (IMC-180C type, manufactured by Imoto Seisakusho Co., Ltd.), and Cr of the original film was 0.85 × 10 ⁻⁹ Pa. ^-1 .

(Production Example 2)
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, a nitrogen introduction tube, and a dropping funnel, MHMA 20 parts, MMA 35.6 parts, MA 13.3 parts, NVCz 8.5 parts, toluene 19.9 parts and methanol 2.7. Prepared the department. While introducing nitrogen gas into the reaction vessel, the temperature was raised to 95 ° C., and when refluxing was started, t-amylperoxy-2-ethylhexanoate (manufactured by Arkema Yoshitomi, trade name: Luperox 575) was used as a polymerization initiator. At the same time, dropwise addition of a mixture of 18 parts MHMA, 32 parts MMA, 50 parts toluene and 0.11 parts t-amylperoxy-2-ethylhexanoate was started. While this mixture was added dropwise over 8 hours, solution polymerization was performed at about 90 ° C. to 100 ° C. under reflux.

Using the obtained copolymer solution, the cyclization condensation reaction, the devolatilization step and the pelletization were performed in the same manner as in Production Example 1 to obtain an acrylic resin pellet (A-2) having a ring structure in the main chain. . The weight average molecular weight was 107,000. The obtained acrylic resin pellets were melt-pressed at 240 ° C. and 30 MPa for 5 minutes using a pressing machine, and the Cr of the original film was 0.34 × 10 ⁻⁹ Pa ⁻¹ .
<Manufacture of amorphous ester polymer>
(Production Example 3)
A mixture of 68.4 parts of TPA, 14.6 parts of EG and 16.9 parts of CHDM was charged into a stainless steel vessel equipped with a stirrer, nitrogen inlet, vacuum port and methanol distillation condenser, and zinc octylate (Nippon Chemical Co., Ltd.) was used as the polymerization catalyst. Industrial, Nikka octix zinc 3.6%) 0.06 part was added, nitrogen was passed at a rate of 100 mL / min, and the temperature was raised to 200 ° C. over 1 hour, then raised to 250 ° C. and 1 The reaction was carried out for 5 hours, and transesterification was carried out while distilling out the methanol produced as a result of the reaction. From the time when the distillation of methanol was completed, the pressure was reduced from normal pressure to high vacuum, and a polymerization reaction was carried out for 1 hour from the time when the pressure reached 0.9 kPa. The molten polymer was extruded into cooling water in the form of a strand from the bottom of the reactor and cut using a strand cutter to pelletize the polymer. When the melting point of the obtained polymer was measured, the melting point was not observed, and it was found that the obtained polymer was an amorphous polymer. The resulting amorphous ester polymer (B-1) had a weight average molecular weight of 2800.

(Production Example 4)
A polymer was obtained in the same manner as in Production Example 3 except that 78.4 parts of TPA, 10.0 parts of EG, and 11.6 parts of CHDM were used. When the melting point of the obtained polymer was measured, the melting point was not observed, and it was found that the obtained polymer was an amorphous polymer. The resulting amorphous ester polymer (B-2) had a weight average molecular weight of 7,500.

(Production Example 5)
A polymer was obtained in the same manner as in Production Example 3 except that 62.4 parts of TPA, 37.5 parts of EG, and 0.11 part of calcium acetate were used as a polymerization catalyst. When the melting point of the obtained polymer was measured, the melting point was observed at 236 ° C., and it was found that the obtained polymer was a crystalline polymer. The obtained crystalline ester polymer (B-3) is insoluble in the GPC developing solvent, and since the weight average molecular weight is not required, the average molecular weight was calculated from the amount of methanol produced and the amount of EG distilled. The reaction molar ratio of TPA / EG was 2/3, and the calculated average molecular weight was 446.

Example 1
95 parts of the acrylic resin pellets (A-1) produced in Production Example 1 and 5 parts of the amorphous ester polymer pellets (B-1) obtained in Production Example 3 were dry blended, and a twin-screw extruder was used. The mixture was melt kneaded at a barrel temperature of 250 ° C. and filtered through a leaf disk type polymer filter (manufactured by Nagase Sangyo, filtration accuracy of 5 μm) to obtain pellets. The pressure increase of the polymer filter was not confirmed.

Further, the pellet obtained from the melt-kneaded resin was melt-extruded under the following conditions using a single screw extruder to produce an unstretched optical film (C-1) having a thickness of 150 μm. The bleed-out property was ○. The obtained optical film had a Tg of 125.4 ° C. In addition, the obtained optical film is roll shape, The width direction of the roll in the said film is made into TD direction, and let the extending | stretching direction (direction orthogonal to TD direction in a film surface) be MD direction.
Cylinder temperature: 240 ° C
Die: Coat hanger type, width 150mm, temperature 260 ° C
Casting: 2 rolls with gloss, 1st roll and 2nd roll are kept at 110 ° C. No fuming or foaming is observed at the time of melt extrusion molding, and the surface condition of the obtained optical film is observed. I couldn't see it. Moreover, after producing an optical film, although the state of the casting roll surface was confirmed visually, the deposit | attachment etc. to a casting roll were not confirmed. The obtained optical film (C-1) has a light transmittance of 92.0%, a haze of 0.7, and Cr of 0.96 × 10 ⁻⁹ Pa ^−1, which is based only on the acrylic resin (A-1). The Cr increase rate was 2.6% when 1% by mass of the amorphous ester polymer (B-1) was contained with respect to Cr of the original film.

  Subsequently, the obtained optical film (C-1) was stretched in the MD direction at a temperature equal to or higher than Tg by uniaxial biaxial stretching. Specifically, the distance between chucks when setting the film on the test apparatus is 80 mm, the film set on the chuck is preheated at 130 ° C., which is Tg + 5 ° C. for 3 minutes, and then stretched at 100% / min. The film was stretched in one direction at a speed so that the stretching ratio was doubled to obtain a retardation film. The in-plane retardation Re of the obtained retardation film was 384 nm.

(Example 2)
95 parts of the acrylic resin pellets (A-2) produced in Production Example 2 and 5 parts of the amorphous ester polymer pellets (B-1) obtained in Production Example 3 were dry blended and the same as in Example 1 Was pelletized. The pressure increase of the polymer filter was not confirmed. Then, using this pellet, a melt film was formed in the same manner as in Example to obtain an unstretched optical film (C-2). No bleed out was observed during film formation. The obtained optical film (C-2) had a Tg of 124.8 ° C., a light transmittance of 92.0%, a haze of 0.7, and Cr of 0.43 × 10 ⁻⁹ Pa ⁻¹ , an acrylic resin The Cr increase rate in the case of containing 1% by mass of the amorphous ester polymer (B-1) with respect to Cr of the original film consisting only of (A-2) was 5.3%.

Subsequently, the obtained optical film (C-2) was stretched uniaxially and twice in the MD direction at a temperature of Tg or higher. Specifically, the distance between chucks when setting the film on the test apparatus is 80 mm, the film set on the chuck is preheated at 130 ° C., which is Tg + 5 ° C. for 3 minutes, and then stretched at 100% / min. The film was stretched in one direction at a speed so that the stretching ratio was doubled to obtain a retardation film. The in-plane retardation Re of the obtained retardation film was 171 nm. Further, wavelength dispersion Re (447) / Re (590) was 0.92.
(Comparative Example 1)
97.4 parts of the acrylic resin pellet (A-1) produced in Production Example 1 and bis (2-ethylhexyl) phthalate as an ester compound (DOP, molecular weight 391) (B-4) 2 manufactured by Daihachi Chemical Industry Co., Ltd. 6 parts were dry blended and pelletized as in Example 1. The pressure increase of the polymer filter was not confirmed. Then, using this pellet, a melt film was formed in the same manner as in Example to obtain an unstretched optical film (C-3). After the film was created, the surface was visually observed, and many deposits were confirmed on the film surface. The obtained optical film (C-3) has a Tg of 125.5 ° C., a light transmittance of 92.0%, a haze of 0.7, and Cr of 0.85 × 10 ⁻⁹ Pa ⁻¹ , an acrylic resin The Cr increase rate was 0% when 1 mass% of the ester compound (B-4) was contained with respect to Cr of the original film consisting only of (A-1).

  Subsequently, the obtained optical film (C-3) was stretched uniaxially and twice in the MD direction at a temperature of Tg or higher. Specifically, the distance between chucks when setting the film on the test apparatus is 80 mm, the film set on the chuck is preheated at 131 ° C., which is Tg + 5 ° C. for 3 minutes, and then stretched at 100% / min. The film was stretched in one direction at a speed so that the stretching ratio was doubled to obtain a retardation film. The in-plane retardation Re of the obtained retardation film was 340 nm.

(Comparative Example 2)
95 parts of the acrylic resin pellets (A-1) produced in Production Example 1 and 5 parts of the amorphous ester polymer pellets (B-2) obtained in Production Example 4 were dry-blended and the same as in Example 1 Was pelletized. The pressure increase of the polymer filter was not confirmed. Then, using this pellet, a melt film was formed in the same manner as in Example to obtain an unstretched film (C-4). The Tg of the film (C-4) was 127.0 ° C. It was confirmed by visual inspection after film formation that the acrylic resin and the ester polymer were not compatible with each other, so that the film became cloudy and was not suitable as an optical film.

(Comparative Example 3)
95 parts of the acrylic resin pellets (A-1) produced in Production Example 1 and 5 parts of the crystalline ester polymer pellets (B-3) obtained in Production Example 5 were dry-blended. Pelletization was performed. The pressure increase of the polymer filter was not confirmed. Then, using this pellet, a melt film was formed in the same manner as in Example to obtain an unstretched film (C-5). The Tg of the film (C-5) was 129.1 ° C. It was confirmed by visual inspection after film formation that the acrylic resin and the ester polymer were not compatible with each other, so that the film became cloudy and was not suitable as an optical film.

(Comparative Example 4)
In Example 1, an attempt was made to obtain a resin composition that had undergone a filtration step without adding an amorphous ester polymer to the acrylic resin pellets (A-1). The resin composition which passed through can not be obtained.

  Table 1 shows the evaluation results of Examples and Comparative Examples. In Examples 1 and 2, it became clear that the inclusion of a specific amorphous ester polymer not only improved the fluidity of the resin composition at the time of melting, but also improved the retardation characteristics. .

The optical film of the present invention has few defects due to bleed-out, and is suitably used as an optical member for image display devices such as liquid crystal display devices (LCD) and organic displays (OLED), particularly as a retardation film. it can.

Claims (8)

  Acrylic resin composition comprising 90 to 99.5 parts by mass of an acrylic resin (A) having a ring structure in the main chain and 0.5 to 10 parts by mass of an amorphous ester polymer (B) having a weight average molecular weight of 500 to 5,000. An optical film comprising:   The optical film according to claim 1, wherein the amorphous ester polymer (B) is an ester having an aromatic ring structure.   The optical film according to claim 1, wherein the amorphous ester polymer (B) is an ester having an alicyclic structure.   The optical film according to any one of claims 1 to 3, wherein a total light transmittance measured in accordance with JIS K7361-1 is 80% or more, and a haze measured in accordance with JIS K7136 is 5% or less.   It is a stretched film, The optical film of any one of Claims 1-4.   It is a retardation film, The optical film of any one of Claims 1-5.   Re (447) / Re (590) <1 The retardation film according to any one of claims 1 to 6, wherein Re (447) and Re (590) each have a measurement light wavelength of 447 nm, It is the in-plane retardation of the optical film measured at 590 nm.   The method for producing an optical film according to any one of claims 1 to 7, wherein the acrylic resin composition having undergone a melt filtration step is melt-formed.